The field of this disclosure relates generally to a diffuser for use in an air handling system, and more specifically, to a diffuser for directing and expanding the cross-sectional area of an airstream circulating in a heating, ventilating, and air conditioning (HVAC) system.
Some HVAC systems include portions of the system that increase the cross-sectional area of the airstream, such as where the airstream exits a blower assembly. However, as the area of the airstream increases, the velocity decreases, i.e., the downstream air loses momentum. Since airstream pressure is inversely proportional to airstream velocity, the pressure in the airstream increases as the velocity decreases. This non-ideal expansion and subsequent increases in pressure generate adverse flow structures. The term “adverse flow structures” designates flow structures in an airstream that have negative effects on HVAC system operation, such as recirculation, vortexes, turbulence, and eddies. These adverse flow structures and the increased pressure result in energy losses for the HVAC system and, therefore, decrease the efficiency of the system. The energy losses are more pronounced in HVAC systems without expansion or transition pieces to optimally change the cross-sectional area of the airstream.
Diffusers are commonly used as expansion or transition pieces for expanding the cross-sectional area of airstreams flowing through HVAC systems. Diffusers are coupled with exhaust outlets or duct sections. Instead of an immediate change in cross-sectional area, traditional diffusers use an inclined wall to gradually change the cross-sectional area. However, in some HVAC systems the airstream separates from the inclined wall causing areas of low pressure, i.e., vacuum pockets, along the inclined wall. Higher-pressure air recirculates to fill the vacuum pockets, resulting in the generation of unfavorable flow structures in the airstream.
Additionally, it is sometimes necessary to change the direction of an airstream in an HVAC system at the same location as a change in cross-sectional area, for example, when the airstream exits the blower assembly. The change in direction also causes the airstream to separate from a wall of the HVAC system and the separation generates unfavorable flow structures.